Drive means for deformable medium carrying member within an evacuated envelope



J1me 1966 F. A. ROMANO, JR 3,

DRIVE MEANS FOR DEFORMABLE MEDIUM CARRYING MEMBER WITHIN AN EVACUATED ENVELOPE Filed Oct. 30, 1962 mmmmm MODULA TION SOURCE INVENTORI FRANK A.

OMANOJR, BY?

Hl TTORNEY.

United States Patent DRIVE MEANS FOR DEFORMABLE MEDIUM CAR- RYING MEMBER WITHIN AN EVACUATED EN- VELOPE Frank A. Romano, .Ir., Syracuse, N.Y., assignor to General Electric Company, a corporation of New York Filed Oct. 30, 1962, Ser. No. 234,144 2 Claims. ("(Il. 313-91) The present invention relates to electron discharge device vacuum enclosures of the permanently sealed or semi-permanently sealed type, and to means for providing mechanical motion in such evacuated environments. More particularly the invention relates to improved means utilizing electric power for providing mechanical drive of a rotatable member in an environment evacuated to a degree suitable for electron beam formation and utilization.

Information display systems are known which involve modulation of the brightness, or color and brightness, of light by variation of the light dilfractive action in a thin layer or film of a viscous fluid medium in accordance with a pattern of electric charge formed thereon under the control of information signals. One information display system utilizing this principle is described in the U.S. patent to W. E. Glenn, Reissue 25,169, commonly assigned herewith.

One of the problems in the operation of such information display systems employing charge-deformable media is that in order to obtain lengthened operating life it is desirable to continually renew the surface of the deformable medium exposed to the charge deposition action, and hence some means is desired for slowly but continuously moving a fresh layer of the deformable medium into'the area or field where the charge deposition action takes place. It has further been found that the rate at which a fresh surface or layer of the deformable medium should be advanced into the charge deposition area is largely dependent upon its viscosity and radiation stability, and without incurring undesired variation in light modulating properties of the medium can be very low. For example, this rate of movement of the deformable medium can be of the order of one inch per hour of operating life. It is also desirable of course-to take maximum advantage of this low permissive rate of surface renewal so as to conserve the total quantity of deformable medium required for a given operating lifetime.

To'produce such movement of the deformable medium various systems have been contemplated, such as embodiments wherein the deformable medium is a liquid and is pumped or otherwise slowly flowed in a film of desired thickness across a stationary supporting substrate, and embodiments wherein a supporting substrate bearing a suitable layer of the deformable medium is itself moved so as to bring a fresh surface into the area where charge deposition takes place.

However the foregoing unusual requirements render conventional driving means unsuitable, particularly from the standpoint of obtaining desired long operating life of the order of several thousand hours. Electric motors disposed within the vacuum environment are undesirable, for example, because of the difliculty of outgassing such motors sufiiciently to avoid later contamination of the evacuated environment by gases gradually evolved from the various parts of the motor, and the difliculty of providing field windings capable of withstanding outgassing bakeout temperatures. Moreover the gases and other contaminants produced from lubricants usually found in electric motors would quickly contaminate the evacuated environment and poison the electron emissive cathode thereof, so that such driving mechansms are not suit-.

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or other mechanical couplings extending through the Wall of the vacuum enclosure are impractical because of the difliculty of maintaining an adequately vacuum-tight seal for such wall-penetrating members during lengthy operating life. Driving arrangements employing coupling of permanent magnets are undesirable because of the interaction between the stray magnetic fields they involve and the inherently magnetic field-sensitive process of electric charge deposition on the deformable medium.

Accordingly it is a principal object of the present invention to provide animproved source ofmechanical motion suitable for long life operation in an environment evacuated sufficiently for formation and utilization of electron beams, and capable of providing continual renewal of a layer of a deformable viscous fluid medium in an electron beam target area, at desired rates.

Another object is to provide a mechanical motion source of the foregoing character which is electrically controllable in speed and direction from outside the evacuated environment.

Another object is to provide driving means of the foregoing character which is mechanically simple, dependable, inexpensive, and capable of operating for prolonged periods without breakdown or need for repairs.

Another object is to provide electrically powered driving means for producing mechanical movement in an environment evacuated to a degree suitable for the emission of electrons from a cathode and the formation and utilization of electron beams, and whose parts disposed in the evacuated environment are easily outgassed prior to sealing.

These and other objects of the invention will be apparent from the following description taken in conjunction with the accompanying drawing wherein:

FIGURE 1 is a schematic illustration of an information display system with which the present invention is particularly suitable; and

FIGURE 2 is an enlarged partially sectionalized view of one form of driving means constructed in accordance with the present invention and particularly adaptable for use with the apparatus of FIGURE 1.

Referring to the drawing FIGURE 1 is a schematic representation of an information display system of a type with which the present invention is particularly suitable. An envelope 2 forms a vacuum enclosure within which an electron beam, generated by an electron gun 4 and controlled in intensity and deflection by appropriate control signals supplied to terminals 6, 8, 10, is caused to deposit a desired pattern of electric charge on a film or layer of a deformable medium or diffraction fluid 12 carried by a moveable substrate shown as a rotatable disc 14, the disc 14 including a bearing 18 and being rotatably mounted to a fixed support member 15 by a pivot pin 17 as shown more clearly in FIGURE 2. The charge deposition or raster area on the disc is shown at 16, the raster area being displaced from the center of the disc 14 so that the pivot pin 17 does not interfere with the raster. Ball bearing 19 may be interposed between the disc 14 and support member 15 to insure vibration free rotation. As described in detail in the aforementioned Reissue Patent 25,169 to W. E. Glenn, a suitable optical system is provided for projecting light from a source 20 through the deformable medium or diffraction fluid 12, 'the deformable medium providing a variable light diffractive action under the control of deposited electric charge. A cooperating schlieren optical system including a set of input bars and slits 24, a set of output bars and slits 28, a schlieren lens 32 for imaging the input slits on the output bars, and an output projection lens 36 serves to reproduce on a screen 40 an image corresponding to the information placed by electric charge deposition on the deformable medium 12.

As previously stated, in an information display system of the type illustrated in FTGURE 1 it has been found desirable to continually renew the film or layer 12 of deformable medium in the electric charge deposition or raster area 16, and for this purpose, when as shown the deformable medium is supplied in a liquid state, the disc 14 is arranged for rotation in a pool 44 of the deformable medium contained within a cup 48 and of such depth as to immerse a substantial portion of the lower half of the disc 14. Thus rotation of the disc 14 coats the immersed portion with the deformable medium 12 and continually moves a freshly coated portion of the disc 14 into the electric charge deposition area 16.

For driving the disc 14 or other equivalent deformable medium or diffraction fluid renewing means in accordance with the present invention I provide an electric motor 30 having certain specialized characteristics, and so constructed and arranged with respect to the vacuum environment that a portion of the motor is situated inside the vacuum enclosure 2 and the remainder of the motor is mounted outside the vacuum enclosure. The electric motor 30 includes a rotor 31 rotatably mounted within a casing 34 of a non-magnetic metal or alloy. The casing 34 is directly sealed, with a vacuum tight seal such as by brazing 35, or welds or the like, to an inwardly extending flange or metal wall portion 37 of the vacuum enclosure at a rotor opening therein, so that the casing 34 of the motor closes the rotor opening in vacuum enclosure 2 and in effect provides a continuation of the wall of the enclosure 2.

Preferablythe motor 30 is of a type having an all metallic rotor portion, without winding insulation or other non-metallic parts which are difficult to bake or otherwise subject to extraction of sorbed gases. For example the motor may be an induction motor of the squirrel cage type, wherein the rotor is entirely metallic, and the preferred embodiment of the motor shown is a single phase alternating current hysteresis-type synchronous motor having a ferromagnetic rotor directly mounted on a rotatable shaft 33 journaled in and projecting from an interior partition 42, rotor 31 and shaft 33 being of entirely metallic construction suitable for withstanding a prolonged outgassing bakeout at high temperatures of, for example, 400 C. Such rotor construction insures that the rotor portion of the motor will evolve a minimum of gas or other contaminants into the vacuum chamber during prolonged operating life of the motor in the evacuated environment.

The stator or stationary armature 41 of the motor is disposed entirely outside the casing 34, and hence entirely exterior to the vacuum enclosure 2. The stator includes a plurality of laminated ferromagnetic pole pieces 45, 46, mounted directly on casing 34. The pole pieces 45, 46 may be equipped with pole shading coils 49, as shown, or other conventional means for providing enhanced starting torque, if desired.

Speed reduction of the rotor shaft 33 may conveniently be provided through a gear train 61, which if desired may be directly housed in an inward extension of the motor casing 34 on the opposite side of partition 42 from rotor 31, and may serve as a mechanical driving connection between the rotor 31 and the output driving pinion 64 of the motor. Suitable mechanical driving connection between the output driving pinion 64 and the disc 14 is provided for example by a gear train including gears 68 .and 72, and shaft 70.

Further in accordance with the invention, contamination of the evacuated environment within enclosure 2 by motor lubricants is minimized by providing for whatever lubrication is needed by the motor moving parts in a manner as compatible as possible with the requirements of the evacuated environment. To this end the moving parts of the motor are preferably lubricated solely with high temperature solidified lubricants having the 4- property of evolving a minimum of gas at the high temperatures involved in outgassing the vacuum system prior to sealing. For example a high temperature solid lubricant such as molybdenum disulfide is preferred, and other low gas-evolving lubricants such as Teflon and prevacuum-fired graphite may also be used.

Where additional lubrication material of a liquid nature is desired or required, it is a particular feature of the present invention that such liquid be entirely miscible with the deformable medium or diffraction fluid. The term miscible is defined and intended in this description to mean broadly that no significantly deleterious effect on the light ditfractive, chemical, electrical, or radiation resistive properties of the diffraction fluid 12 results from contamination thereby with the liquid lubricant from the motor, and that the motor liquid lubricant is not significantly more toxic to the cathode of the electron gun than the diffraction fluid 12 itself. Thus I prefer to use as such liquid lubricant for motor a liquid or liquified form of the same material which serves as the deformable medium 912.

Various materials for the diffraction fluid or deformable medium 12 may be used within the contemplation of the present invention. By way of illustration, desirable properties of such materials are high resistance to destruction or excessive polymerization under electron beam exposure, a viscosity in the operating temperature range (50 C. to 100 C.) of about 500 to 1500 centistokes, a resistivity of about 10 to 10 ohm cm., and a dielectric constant of about 3.0. A number of exemplary diffraction fluids suitable for medium 12 are listed in US. Patent 2,943,147, commonly assigned herewith, and include, for example, methyl silicone fluids, and methyl phenyl silicone fluids. Other exemplary materials are polybenzyl benzene and polybenzyl toluene. A small quantity, e.g., 0.5 cc., of such diffraction fluid present within the motor casing 34- and at such points as the bearing of shaft 33 in partition 42 have been found entirely satisfactory as a long life lubricant miscible with the ditfraction fluid at raster 16, and suitably nontoxic to the cathode of electron gun 4.

When the viscosity of the diffraction fluid 12 or other liquid or liquifiable lubricant miscible with diffraction fluid 12, is such that at the normal operating temperature within the motor casing 34 the liquid lubricant is excessively viscous, suitable additional heating means such as an electric resistance heater 60 may be provided to raise the temperature and thereby reduce the viscosity of the liquid lubricant sufficiently for enhanced lubrication. When liquid lubrication of the motor is desired, conveniently a charge of the diffraction fluid 12, or other liquid or liquifiable lubricant miscible with diffraction fluid 12, may be placed within the motor casing 34 prior to sealing of the vacuum enclosure 2. Subsequent heat treating of the assembled structure to outgas the parts,

thereof may result in some diminution of the quantity of the lubricant charge within the motor casing 34, and hence this factor should be taken into account in selecting the amount of diffraction fluid-miscible lubricant to be placed within the motor casing 34 prior to sealing and the outgassing heat treatment. Solid lubricants such as molybdenum disulfide may also be mixed with the liquid lubricants in the motor casing 34, for example by direct dispersion of the solid lubricant in the liquid lubricant.

It will be appreciated by those skilled in the art that the invention may be carried out in various ways and may take various forms and embodiments other than the illustrative embodiments heretofore described. Accordingly it is to be understood that the scope of the invention is not limited by the details of the foregoing description, but will be defined in the following claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination with an electron discharge device having an evacuated enclosure, means providing an electron beam Within said enclosure, a moveable member within the enclosure arranged to be driven, and a layer of a light diffractive deformable medium carried by said moveable member and arranged to be scanned by said electron beam, driving means for said moveable member including an electric motor having a metal casing sealed to said enclosure and forming a non-apertured vacuum tight portion of the wall of said enclosure, said motor having a substantially entirely metallic rotor portion within said casing, and a stator portion mounted on the outside of the casing, means forming a driving connection between said driven member and said rotor, and a rotor lubricant within said casing miscible With said deformable medium.

2. In combination with an electron discharge device having an evacuated enclosure, means providing an electron beam within the enclosure, a moveable member within the enclosure arranged to be driven, and a layer of a light ditfractive deformable medium carried by said moveable member and arranged to be scanned by said electron beam, driving means for said moveable member including a hysteresis-type single phase synchronous induction motor having a metal casing sealed to said enclosure and forming a non-apertured vacuum tight portion of the wall of said enclosure, said motor having a substantially entirely metallic rotor portion mounted for rotation inside said casing and a stator portion disposed outside the casing, means forming a driving connection between said driven member and said rotor portion, and a rotor lubricant within said casing miscible with said deformable medium.

References Cited by the Examiner GEORGE N. WESTBY, Primary Examiner.

V. LAFRANCHI, Assistant Examiner. 

1. IN COMBINATION WITH AN ELECTRON DISCHARGE DEVICE HAVING AN EVACUATED ENCLOSURE, MEANS PROVIDING AN ELCTRON BEAM WITHIN SAID ENCLOSURE, A MOVEABLE MEMBER WITHIN THE ENCLOSURE ARRANGED TO BE DRIVEN, AND A LAYER OF A LIGHT DIFFRACTIVE DEFORMABLE MEDIUM CARRIED BY SAID MOVEABLE MEMBER AND ARRANGED TO BE SCANNED BY SAID ELECTRON BEAM, DRIVING MEANS FOR SAID MOVEABLE MEMBER INCLUDING AN ELECTRIC MOTOR HAVING A METAL CASING SEALED TO SAID ENCLOSURE AND FORMING A NON-APERTURED CACUUM TIGHT PORTION OF THE WALL OF SAID ENCLOSURE, SAID MOTOR HAVING A SUBSTANTIALLY ENTIRELY METALLIC ROTOR PORTION WITHIN SAID CASING, AND A STATOR PORTION MOUNTED ON THE OUTSIDE OF THE CASING, MEANS FORMING A DRIVING CONNECTION BETWEEN SAID DRIVEN MEMBER AND SAID ROTOR, AND A ROTOR LUBRICANT WITHIN SAID CASING MISCIBLE WITH SAID DEFORMABLE MEDIUM. 